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Chacabucogod
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A propeller shaft in the largest and most powerful ships transmits about 50,000 hp (1HP=33,000 ft*lb/min). Assume that the propeller transforms this power into a forward push on the ship with an efficiency of 70 per cent and that the ship's speed then is 30 knots (1 knot is 6,080 ft/hr).
The shaft is 300 ft long from the propeller to the thrust bearing in the engine room, where the thrust is transmitted to the ship's hull structure. The diameter of the (solid, circular) shaft is 24 in. Calculate the elastic contraction of the shaft at full power. (Answer:0.985 in).
There is no number for E provieded. So I assumed it's 30,000,000 lb/in^2. Maybe that's where the problem lies.
[tex]\Delta l=\frac{FL}{EA}[/tex]
[tex]Power=F*v[/tex]
Power=[itex]1.65x10^9 \frac{ft*lb}{min}[/itex]
[itex]speed=182,400\frac{ft}{hr}[/itex][tex]50,000*33,000*0.7=v*182,400*\frac{1 hour}{60 min}[/tex]
F=379.934x10^3 lb
[tex]\frac{379.934x10^3*300*12}{144\pi *30,000,000}[/tex]
Ans=0.105 in
The shaft is 300 ft long from the propeller to the thrust bearing in the engine room, where the thrust is transmitted to the ship's hull structure. The diameter of the (solid, circular) shaft is 24 in. Calculate the elastic contraction of the shaft at full power. (Answer:0.985 in).
There is no number for E provieded. So I assumed it's 30,000,000 lb/in^2. Maybe that's where the problem lies.
Homework Equations
[tex]\Delta l=\frac{FL}{EA}[/tex]
[tex]Power=F*v[/tex]
Power=[itex]1.65x10^9 \frac{ft*lb}{min}[/itex]
[itex]speed=182,400\frac{ft}{hr}[/itex][tex]50,000*33,000*0.7=v*182,400*\frac{1 hour}{60 min}[/tex]
F=379.934x10^3 lb
[tex]\frac{379.934x10^3*300*12}{144\pi *30,000,000}[/tex]
Ans=0.105 in